for induction just get a panel filter and modifiy the airflow to 70mm hosing run down to the vent next to the horn.some people will say drill the wingside and front bottom part of the airboxtoo,others disagree.
open cone filters are a waste of time and money as they just suck in hot air.
lowering for £200?
I'd go ( and did) for Eibach springs on standard shocks for @£100-130 ( perfectly ok to do although again some disagree but i've had mine on for 18 months with no probs and eibach themselves say its not a problem). withthe left over cash get the tracking and camber reset as it will be out.